The present disclosure relates to a combustor and, more particularly, to a conjoined grommet assembly for a combustor of a gas turbine engine.
Gas turbine engines, such as those that power modern commercial and military aircraft, include a fan section to propel the aircraft, a compressor section to pressurize a supply of air from the fan section, a combustor section to burn a hydrocarbon fuel in the presence of the pressurized air, and a turbine section to extract energy from the resultant combustion gases and generate thrust.
The combustor section typically includes a wall assembly having an outer shell lined with heat shields that are often referred to as floatwall panels. Together, the panels define a combustion chamber. A plurality of dilution holes are generally spaced circumferentially about the wall assembly and flow dilution air from a cooling plenum and into the combustion chamber to improve emissions, and reduce and control the temperature profile of combustion gases at the combustor outlet to protect the turbine section from overheating. To ensure a satisfactory temperature profile at the chamber outlet, there must be adequate penetration of the dilution air, coupled with the correct number of dilution holes to form sufficient localized mixing zones in the chamber. The penetration of a round dilution hole is generally a function of its diameter. That is, if the total dilution hole area is spread over a large number of small holes, penetration will be inadequate, and a hot core (i.e. radial center of combustion chamber) will persist through the dilution zone of the chamber. In the opposite extreme, the use of a small number of large holes will result in a cold core, due to over-penetration and unsatisfactory mixing.
To optimize this outlet temperature profile, the dilution holes are strategically sized and distributed both axially and circumferentially through the wall assembly. Part of this strategic sizing and location of dilution holes must include consideration of combustor chamber pressure differentials, cross flows and minimization of hot spots upon the panels and typically located proximate to the dilution holes. Unfortunately, each dilution hole is generally defined by a distinct and specific grommet that extends between the panel and the shell. Each grommet is traditionally spaced from the other grommets of the adjacent cooling holes. This spacing (i.e. the wall thicknesses of the grommets) limits the orientation or proximity of the dilution holes to one-another.